<?hh
/**
 * Copyright (c) 2014, Facebook, Inc.
 * All rights reserved.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the "hack" directory of this source tree.
 *
 *
 */

class A {
  private ?string $x = null;

  public function test(string $x): string {
    return $this->x = $x;
  }
}
